WELCOMING me into his penthouse flat overlooking London's Chelsea Harbour, Sir Michael Caine is clearly relishing life in his 80s.

Shelves are lined with framed pictures of the award-winning actor and his family – the smiling faces of his three grandchildren, snaps of him holding one of his two Oscars, with his wife Shakira, who is bustling around in the background today.

At 85, he's still making movies, despite breaking his ankle earlier this year – he slipped on some ice during the 'beast from the East', while pottering in the garden at his country home in Surrey. It's taken a while to heal, but he's now walking without a stick again, he enthusiastically reveals.

He's also just written his third book, Blowing The Bloody Doors Off, in which he highlights where he's come from (working-class, never expected to do much) to where he's arrived (stardom, wealth, all-round success) and how he got there (push-backs, heartbreak, good movies, bad movies, dogged determination).

What's different about this one, compared with his previous two autobiographies, is that Caine offers his life lessons to the reader. It's thinly disguised as a guide for actors – learn your lines, turn up on time, have fun, use failures and difficulties to move forward – but the messages can really be adopted by anyone.

Caine is good company. He may have aged, but his brain has stayed sharp, his humour is quick, and that trademark Cockney accent which helped break class barriers in the 1960s remains as recognisable as ever. He laments that Shakira, his wife of 45 years, is going to New York for four days – the longest they'll have ever been apart – to see her mother, who is unwell, and he doesn't quite know what to do with himself.

"I'll go home to the country, watch TV for four days. I'm taking a cook so I don't have to do anything – and I'll probably get a little bit p***ed," he says with a chuckle.

The star of Alfie, The Ipcress File, Get Carter, The Italian Job, Educating Rita, The Cider House Rules and, most recently, King Of Thieves – and more than 100 other films – has lost many great friends in recent times, including Sir Roger Moore who died last year, and reflects that these days, weddings and birthday parties give way to hospital visits and memorial services.

"And each successive death does not get any easier to bear. I have, though, found that as our little group has become smaller and smaller, it has also become closer and closer. I have also enjoyed getting to know my friends' widows better than I did when their husbands were alive," he writes.

Today, he says he never thinks about his own mortality. "I could be sitting here talking you you and then die from a stroke and wouldn't know anything about it at all. My mother lived to 92, one grandfather 94, and another grandfather 96. I might have ten years yet. I live for the day. I don't live for tomorrow and I certainly don't live for yesterday. I say to my kids, 'Don't look back, you'll trip over'. I relish every moment."

He's currently working on Medieval, a war film being shot in the Czech Republic, and is considering a TV comedy series – which he's never done – centring on people in a care home. He also wants to write a novel and has recently returned to a draft which he penned a while ago, about a plane which smashes into a skyscraper. After 9/11 he put it away in a drawer.

Indeed, Maurice Micklewhite (his born name) has come a long way. The son of a Billingsgate Market fish porter and a charlady, he was brought up in a two-room flat with an outside toilet and no hot water, in one of the grottiest areas of London. He survived rickets and poverty as a child, the trenches of Korea as a young soldier, and received a succession of knock-backs when he decided he wanted to act; people told him he'd never be a movie star.

"I became an actor not to be rich and famous. I had a Cockney accent, wasn't very good-looking, there was no hope for me. All I set out to do was to become the best actor that I could be."

Of course, he proved his detractors wrong long ago. And while many of his movies were turkeys, he regrets nothing. Jaws: The Revenge, one of his stinkers, paid for a very nice house for his mum, he reflects.

He says the Sixties revolution altered the course of his life, when working-class heroes and angry young men became fashionable in the movies. "I became a movie star not because I wasn't like you, but because I was. Working-class actors became stars, if you think in terms of Tom Courtenay, Albert Finney and Sean Connery. Writers started to write about the working class."

His family is now his top priority. "Family is everything. Shakira's incredible. We've been married 45 years and haven't had a row yet. The secret of a happy marriage is separate bathrooms," he states with a laugh, adding that his grandchildren keep him young.

"You grow old and one day you think, 'I'm going to die soon'. Then you have grandchildren and you forget all about that. Your whole life starts again."

Blowing The Bloody Doors Off: And Other Lessons In Life by Michael Caine (Hodder & Stoughton, £20)